Laser level

ABSTRACT

A light detector which includes a housing having front and rear walls, a light receiving section disposed on the front wall, and displays disposed on the front and rear walls for showing the location of received light relative on the light receiving section. Also disclosed is a laser level including a motor, a shaft driven by the motor, a housing fixedly disposed on the shaft, the housing having a bore therein, a barrel pivotally connected to the housing, a laser diode module disposed within the barrel, and a screw disposed on the housing and contacting the barrel for adjusting the pivotal position of the barrel.

BACKGROUND OF INVENTION

[0001] Laser levels have been used in construction for many years. Theytypically seek to produce a plane of light for a reference forconstruction projects. Laser levels have been used for large scaleconstruction projects like commercial excavating, laying foundations,and installing drop ceilings. Laser levels save considerable time duringinitial layout of a construction job compared to other tools such asbeam levels, chalk lines, or torpedo levels. Some examples of jobs wherelaser levels would be useful include laying tile, mounting cabinets,installing counter tops, and building outdoor decks. Because these laserlevels can typically cost thousands of dollars, only those who regularlyland larger construction projects can justify purchasing a laser level.Laser levels have not achieved widespread adoption by the general publicdespite the time savings because of their initial cost of ownership. Theexpense can be attributed to the cost of suitable laser sources such asHe-Neon laser and associated optical system used to manipulate the beamgenerated by the laser source.

SUMMARY OF INVENTION

[0002] In accordance with the present invention, an improved laser levelis employed. The laser level comprises a motor, a shaft driven by themotor, a housing fixedly disposed on the shaft, the housing having abore therein, a barrel pivotally connected to the housing, a laser diodemodule disposed within the barrel, and a screw disposed on the housingand contacting the barrel for adjusting the pivotal position of thebarrel.

[0003] Also disclosed is a light detector, which comprises a housinghaving front and rear walls, a light receiving section disposed on thefront wall, and displays disposed on the front and rear walls forshowing the location of received light relative on the light receivingsection.

[0004] Additional features and benefits of the present invention aredescribed, and will be apparent from, the accompanying drawings and thedetailed description below.

BRIEF DESCRIPTION OF DRAWINGS

[0005] The accompanying drawings illustrate preferred embodiments of theinvention according to the practical application of the principlesthereof, and in which:

[0006]FIG. 1 is a side view of a laser level according to the invention;

[0007]FIG. 2 is a partial cross-sectional view along line A-A of FIG. 1,where FIGS. 2A-2B show two different embodiments;

[0008]FIG. 3 is a bottom plan view of the laser level;

[0009]FIG. 4 is a cross-sectional view along line B-B of FIG. 3;

[0010]FIG. 5 is a top plan view of the show assembly;

[0011]FIG. 6 is a partial top plan view along line C-C of FIG. 1;

[0012]FIG. 7 illustrates a clamp assembly, where FIGS. 7A-B show theclamp assembly in the open and closed positions, respectively, and FIG.7C is a partial top plan view along line A-A of FIG. 7A;

[0013]FIG. 8 illustrates the engine assembly, where FIGS. 8A-D are rightside, rear, front and left side views, respectively;

[0014]FIG. 9 is a first engine assembly locking mechanism;

[0015]FIG. 10 is a second engine assembly locking mechanism;

[0016]FIG. 11 is a rear view of a multi-battery adapter assembly;

[0017]FIG. 12 is a partial cross-sectional view of the multi-batteryadapter assembly along line A-A of FIG. 11;

[0018]FIG. 13 illustrates a battery ejector assembly, where FIGS. 13A-Care partial cross-sectional views of the assembly;

[0019]FIG. 14 is a top plan view of the engine assembly;

[0020]FIG. 15 is a partial front view of a laser assembly along line A-Aof FIG. 8A;

[0021]FIG. 16 is a perspective view of a link of the laser assembly ofFIG. 15;

[0022]FIG. 17 is a cross-sectional view along line A-A of FIG. 15;

[0023]FIG. 18 is a cross-sectional view along line B-B of FIG. 15;

[0024]FIG. 19 is a cross-sectional view along line X-X of FIG. 20;

[0025]FIG. 20 is a cross-sectional view along line D-D of FIG. 8B

[0026]FIG. 21 is an alternate cross-sectional view along line D-D ofFIG. 8B;

[0027]FIG. 22 is a partial top plan view along line E-E of FIG. 8C;

[0028]FIG. 23 illustrates a vial plate of the laser assembly, where FIG.23A is a front view and FIG. 23B is a side view along line A-A of FIG.23A;

[0029]FIG. 24 is a cross-sectional view along line C-C of FIG. 8A;

[0030]FIG. 25 is a cross-sectional view along line B-B of FIG. 8C;

[0031]FIG. 26 is a diagrammatic view of the laser beam;

[0032]FIG. 27 illustrates the bump sensor assembly, where FIG. 27A is abump sensor assembly, FIG. 27B is a circuit schematic of the bump sensorassembly, and FIG. 27C is a bump sensor assembly including a mechanicalamplifier assembly;

[0033]FIG. 28 is a block diagram illustrating a bump sensor circuit;

[0034]FIG. 29 is a circuit schematic of the bump sensor circuit of FIG.28, of which FIGS. 29A-C illustrate different portions of the bumpsensor circuit, where leads B and C in FIG. 29A connect to leads B and Cin FIG. 29C, and lead A in FIG. 29B connects to lead A in FIG. 29C;

[0035]FIG. 30 illustrates a laser level used in conjunction with a lightdetector;

[0036]FIG. 31 is a block diagram illustrating the light detectorcircuit;

[0037] FIGS. 32A-C are diagrammatical plane views illustrating therelation between the measuring light beam and the light-receivingsection;

[0038] FIGS. 33A-C are plane views illustrating display patterns in thedisplay sections;

[0039]FIG. 34 is a top plan view of the laser level used in conjunctionwith the light detector;

[0040]FIG. 35 illustrates the motor speed control circuit, where FIG.35A is a block diagram of the circuit, and FIG. 35B is the circuitschematic for such circuit; and

[0041]FIG. 36 illustrates a light detector according to the invention,where FIG. 36A is a front perspective view thereof, FIG. 36B is a rearperspective view thereof, and FIG. 36C is a partial cross-sectional viewalong line A-A of FIG. 36A.

DETAILED DESCRIPTION

[0042] The invention is now described with reference to the accompanyingfigures, wherein like numerals designate like parts. Referring to FIG.1, a laser level 10 preferably comprises a frame assembly 30, an engineassembly 40 rotatably attached to frame assembly 30, a laser diodeassembly 410 (shown in FIG. 20) disposed within engine assembly 40, aprotective assembly 20 connected to frame assembly 30, a shoe assembly50 slidably attached to protective assembly 20, a clamp assembly 80disposed on shoe assembly 50, and a multi-battery adapter assembly 70for receiving a battery 60. These assemblies are discussed in furtherdetail below.

[0043] Preferably, protective assembly 20 has at least one protectivebar 22 flexibly connected to the frame assembly 30. Such bar 22 may bemade of aluminum, or other suitable material. Preferably, the bar 22 ismade of a plastic, such as ABS or polypropylene. The bar 22 may beinjection-molded. Alternatively, the plastic may be injected into a mold(preferably about half the volume needed to complete fill the mold andthus filling half of the mold), then air or gas is blown therein,pushing the plastic into the other half of the mold, forming a hollowtube. This process is known as gas-assist injection molding.

[0044] The entire protective assembly 20 may be constructed as discussedabove. Preferably, the protective assembly 20 surrounds and/or isdisposed on both sides of frame assembly 30. A handle 21 may be disposedbetween bars 22. Handle 21 may be fixedly attached to the bars 22 via,e.g., screws (not shown).

[0045] Preferably, the shape of protective assembly 20 and handle 21 issuch that the frame assembly 30 and/or engine assembly 40 cannot becontacted by anything wider than the handle 21 and/or protectiveassembly 20. Such construction minimizes the risk of damage to frameassembly 30 and/or engine assembly 40.

[0046] As mentioned above, the protective assembly 20 may be flexiblyconnected to the frame assembly 30. Such connection is achieved via theconnector assemblies 23. Referring to FIG. 2A, a connector assembly 23is disposed between the protective assembly 20 and a wall 31 of framehousing 30. The connector assembly 23 comprises a flexible isolator 23G,which is preferably made of a flexible, resilient material such asrubber or an elastometer. The isolator 23G may be connected to theprotective assembly 20 and wall 31 via a screw 23S, which may extendthrough one of the protective assembly 20 and/or wall 31 and threadinglyengage the other of the protective assembly 20 and/or wall 31.

[0047] Alternatively, a isolator 23G′ may be connected to protectiveassembly 20 via a screw 23S′ extending through the protective assembly20 and entering into isolator 23G′, or vice versa, as shown in FIG. 2B.Screw 23S′ may then threadedly engage a nut 23SN. The isolator 23G′ inturn may be connected to the wall 31 via a screw 31 S extending throughthe wall 31 and entering into isolator 23G′, or vice versa. Screw 31 Smay then threadedly engage a nut 31SN. Isolator 23G′ may be molded overscrews 23S′, 31S and/or nuts 23SN, 31SN. Such construction minimizes theshock received by frame assembly 30 and/or engine assembly 40, and thusby the circuitry and components mounted within, when laser level 10 isdropped.

[0048] Referring to FIGS. 1 and 3-6, shoe assembly 50 may be slidablyconnected to protective assembly 20. Protective assembly 20 may have tworails 24 surrounding shoe assembly 50. Shoe assembly 50 may have a plate51, with tabs 51T extending therefrom. Plate 51 is preferably made ofplastic. Preferably, each rail 24 has a groove 24G for receiving tab51T. Accordingly, shoe assembly 50 can slide relative to protectiveassembly 20 via the groove/tab connection. Persons skilled in the artshould recognize that the same result would be achieved if protectiveassembly 20 and shoe assembly 50 had tabs and channels disposedrespectively thereon.

[0049] Shoe assembly 50 may have at least one rack 51R (and preferablytwo racks 51R) disposed on plate 51. Such rack 51R engages pinion 24Pdisposed on a shaft 24S, which may extend between rails 24.

[0050] Shaft 24S preferably carries rotatable knob 24RK at one end ofthe shaft. Rotatable knob 24RK is fixedly connected to shaft 24S.Accordingly, a user can rotate the pinions 24P by rotating rotatableknob 24RK. As the pinions 24P rotate, the plate 51 will move forwardlyor rearwardly. Travel of plate 51 may be limited by disposing enlargedteeth 51RT at the beginning and/or the end of rack 51R Because pinion24P will not be able to mesh with enlarged teeth 51RT, pinion 24P willnot rotate any further and travel of plate 51 in that direction islimited.

[0051] Shaft 24S may also carry locking knob 24LK at its other end ofthe shaft. Locking knob 24LK may threadingly engage shaft 24S.Accordingly, when a user rotates locking knob 24LK, the knob will pinchrails 24 between locking knob 24LK and rotatable knob 24RK, lockingplate 51 in place. Therefore, the user can fix and lock the shoeassembly 50 relative to protective assembly 20 by rotating locking knob24LK.

[0052] Plate 51 may also have strengthening ribs 51SR for strengtheningthe plate 51. Plate 51 may also have an opening 51O for reducing theweight of and/or the amount of materials used in plate 51. Opening 51Omay also allow viewing of the cast laser beam on a floor or worksurface. Plate 51 may also have a threaded tripod mount 51TM.

[0053] Plate 51 may also have wall mount holes 51WM for receiving atleast one nail or screw mounted on a wall, allowing the user to hang thelaser level 10 from a wall. The verticality of laser level 10 can thenbe adjusted by rotating knob 51K. Knob 51K preferably extends throughand threadingly engages plate 51. A pad 51KP may be disposed at the endof knob 51K. Pad 51KP may be made of plastic or rubber. Pad 51KP may befixed or captured on knob 51K via a screw 51KPS and/or washer (notshown), or may snap into a feature of rotating knob 51K. Accordingly,the distance between plate 51 and the wall may be adjusted by rotatingknob 51K. Because pad 51KP may be free to swivel about knob 51K, it canbe used on uneven or unlevel surfaces.

[0054] Referring to FIGS. 1, 5 and 7, plate 51 may also support clampassembly 80. Clamp assembly 80 may be used for clamping laser level 10onto a ceiling, etc. Preferably, plate 51 has a vertical wall 51W, whichis pivotally connected to clamping wall 81. Clamping wall 81 may haveprotrusions 81P for enhancing the clamping of a surface. Similarly, wall51W may have protrusions (not shown) for enhancing the clamping of asurface. Persons skilled in the art will recognize that a surface willbe clamped between wall 51W and clamping wall 81.

[0055] Preferably, clamp assembly 80 can be opened and closed. This canbe accomplished in different manners. One such manner provides clampingwall 81 with an extension arm 81A, which may be substantiallyperpendicular to wall 81. A shaft 85 may extend through arm 81A and ispivotally connected to a cam 83 via a pin 85P. Persons skilled in theart will recognize that arm 81A may be contacted underneath by the head85H of shaft 85 and/or spring 84, which may be captured between arm 81Aand shoulder 85S of shaft 85. Because of this, arm 81A (and thus wall81) will move when shaft 85 moves upwardly.

[0056] Cam 83 may fixedly attached to shaft 82, which may be rotated bylever 86. Accordingly, when shaft 82 is rotated in one direction, cam 83is rotated is rotated in the same direction, moving shaft 85 upwardly,which in turn moves arm 81A upwardly, rotating clamping wall 81 towardswall 51W. In other words, clamp assembly 80 is thus closed. If shaft 85bottoms out, spring 84 can move arm 81A further.

[0057] Preferably, a torsion spring 81S may be disposed between clampingwall 81 (or arm 81A) and wall 51W. When cam 83 is rotated in the otherdirection, the force pressed onto arm 81A by shaft 85 and/or spring 84is diminished. Torsion spring 81S then forces the wall 81 (or arm 81A)away from wall 51W. In other words, clamp assembly 80 is thus opened.Therefore, clamp assembly 80 may be opened or closed by rotation ofshaft 82.

[0058] It is preferable to provide shaft 82 with a pin 82P travelingalong a channel 51C in plate 51 to limit the range of rotation of shaft82. This prevents a user from overtightening clamp assembly 80.

[0059] Preferably, wall 51W has zero markings 51ZI. Plate 51 may alsohave indicia 51I to indicate the distance between the clamping wall 81and/or wall 51W (or zero marking 51ZI) and the frame assembly 30.Accordingly, the user can precisely determine whether the frame assembly30 and/or engine assembly 40 is at, e.g., two inches from the clampingwall 81 and/or wall 51W.

[0060] As mentioned above, engine assembly 40 is pivotally attached toframe assembly 30, as shown in FIGS. 1 and 8. In other words, engineassembly 40 may be rotated from a substantially vertical position forradiating a laser beam LB along a horizontal plane to a substantiallyhorizontal position (shown in dotted lines) for radiating laser beam LBalong a vertical plane. Persons skilled in the art will recognize that,if the vertical position is 0° and the horizontal position is 90°, it ispreferable to allow rotation of engine assembly 40 from about −5° to140°.

[0061] Referring to FIGS. 1 and 8-10, a shaft 32 extends through frameassembly 30 and engine assembly 40, allowing engine assembly 40 torotate thereabout. Engine assembly 40 may have a rack 49R which mesheswith a pinion 35 supported by frame assembly 30. Accordingly, the usercan precisely rotate engine assembly 40 by rotating pinion 35. It ispreferable to provide a pointer 31P and indicia 42I on wall 31 andengine assembly 40 to indicate the angle of engine assembly 40 relativeto frame assembly 30.

[0062]FIG. 9 illustrates a first locking mechanism for fixing theangular position of engine assembly 40. As mentioned above, shaft 32extends through right wall 31R, engine assembly 40 and left wall 31L. Acam 33 may be pivotally attached to shaft 32 via pin 33P. When a userrotates cam 33 via handle 33H, camming portion 33C increases thedistance between pin 33P and left wall 31L. Such action locks engineassembly 40 by pinching engine assembly 40 between walls 31R, 31L.Alternatively, if engine assembly 40 is fixedly connected, no pinchingis necessary, as the camming portion 33C will prevent rotation of shaft32 until released.

[0063]FIG. 10 illustrates a second locking mechanism for fixing theangular position of engine assembly 40, where like numerals refer tolike parts. As mentioned above, shaft 32 extends through right wall 31R(not shown), engine assembly 40 and left wall 31L. Engine assembly 40 ispreferably fixedly attached to shaft 32. A detent mechanism 34 may bepivotally attached to shaft 32 via pin 34P. Detent mechanism 34preferably has a detent protrusion 34D, which may engage a notch 31N inleft wall 31L.

[0064] Accordingly, the angular position of engine assembly 40 may befixed by the location of the notch 31N engaged by protrusion 34D. Tounfix the angular position, the user needs to move handle 34H untilprotrusion 34D clears notch 31N. The user can then change the angularposition of engine assembly 40.

[0065] Persons skilled in the art should recognize that multiple angularpositions of engine assembly 40 may be available by providing multiplenotches 31N at different angles. Persons skilled in the art shallrecognize that detent protrusion and notches could have been disposedalternatively on the wall 31L and detent mechanism 34 to achieve thesame result.

[0066] Persons skilled in the art should also recognize that it ispreferable to provide a spring 34S between detent mechanism 34(preferably handle 34H) and wall 31L to bias the protrusion 34D intoengagement with notch 31N. Preferably, spring 34S is an extensionspring. Alternatively, spring 34S could be a compression spring ifdisposed in the appropriate manner.

[0067] A preferred embodiment of the engine assembly 40 is shown inFIGS. 15-25. Persons skilled in the art should refer to U.S. Pat. No.5,754,582, which is wholly incorporated by reference herein. Engineassembly 40 may include a laser assembly 400. Laser assembly 400 mayinclude a laser diode assembly 410, a driving assembly 420 for rotatingthe laser diode assembly 410, and a powering assembly 430 for poweringthe laser diodes in the laser diode assembly 410.

[0068] Laser diode assembly 410 preferably includes a laser diodehousing 411, which is preferably made of aluminum. Laser diode housing411 may have two cylindrical bores 412, which are preferably coplanar.(Persons skilled in the art should recognize that the number of bores412 provided may match the number of laser diodes modules disposed inthe housing. In the preferred embodiment, two laser diode modules are tobe disposed in laser diode housing 411, for reasons further explainedbelow.)

[0069] Laser diode assembly 410 may also include a barrel 413 insertedinto each bore 412. Barrels 413 carry the laser diode modules 415.Preferably, the present invention employs a low cost laser diode modulesuch as that used in laser pointers. These laser diode modules include alaser diode source and an optical system 415L disposed on barrel 413,which is preferably made of aluminum. The optical components areinexpensive and the alignment process is quick and simple. A standardlow cost laser diode module consists of a laser diode 415D and a printedcircuit board 415P for mounting the diode 415D. Preferably, diode 415Dis Sanyo part numbers DL-3148-033 or DL-3148-034.

[0070] Printed circuit board 415P may carry a power regulationintegrated circuit for limiting the power sent to laser diode 415Dand/or limiting the brightness of laser diode 415D. One suitable laserdiode module 415 may be the VLM-670 available from Quarton Company ofTaipei, Taiwan. In a typical manufacturing process for these laser diodemodules, the laser diode 415D is glued or soldered to the printedcircuit board 415P.

[0071] In addition, barrel 413 may be pivotally attached to laser diodehousing 411 via a pin 414, which is preferably disposed substantiallyhorizontally. Accordingly, barrel 413 may be adjusted rotationally aboutpin 414, allowing the pitch of barrel 413 to be adjusted. This may beaccomplished by disposing barrel 413 between a spring 417 and a setscrew 416.

[0072] To adjust the barrel 413 (and thus laser diode module 415), theassembler needs only to rotate set screw 416. If screw 416 is rotatedfor downward movement, barrel 413 will move downwardly. On the otherhand, if screw 416 is rotated for upward movement, barrel 413 will moveupwardly due to spring 417. Preferably, set screw 416 is locked in placewith a quick drying adhesive, such as Loc-Tite, etc. Persons skilled inthe art will recognize that this adjustment methodology is preferable sothat the position of the laser diode module 415 is not susceptible todisturbance due to vibration during the transportation of the laserlevel 10.

[0073] Persons skilled in the art will recognize that laser diodehousing 411 may have a bore 417B for receiving spring 417 therein, aswell as a hole 417H for facilitating insertion of spring 417 therein.

[0074] Laser diode housing 411 is preferably disposed on a shaft 419,which may be electrically charged, as explained below. Preferably, shaft419 is made of metal, such as aluminum or steel, and carries a positivecharge. A wire 419P may connect the shaft 419 to the laser printedcircuit board 415P. Alternatively, laser printed circuit board 415P maybe connected to barrel 413, which in turn is electrically connected tolaser diode housing 411 (and shaft 419) via pin 414, screw 416 and/orspring 417.

[0075] Shaft 419 may be hollow to carry a negative wire 415N. Negativewire 415N preferably extends through shaft 419 and barrel 413, and isconnected to the laser printed circuit board 415P.

[0076] Shaft 419 may be rotatably supported by a vial assembly 450,which includes vial plate 451. Preferably, a bearing 419B is disposed onvial plate 451. Bearing 419B may rotatably receive shaft 419therethrough. Persons skilled in the art will recognize that bearing419B minimizes friction between shaft 419 and vial plate 451. Inaddition, bearing 419B may be pre-loaded axially to reduce clearanceswithin the bearing itself. Lack of bearing pre-load may result incalibration drift, affecting the accuracy of laser assembly 400.

[0077] In addition, an insulating layer 419I may be disposed betweenbearing 419B and vial plate 451. In this manner, the electrical chargeof shaft 419 will not be conducted to vial plate 451 and/or vialassembly 450. Alternatively, electrostatic discharge (ESD) from exposedmetal surfaces will not be conducted to the diodes 415D, which may besensitive to ESD.

[0078] It is preferable to provide a cap 418 on laser housing 411 toprevent users from touching and/or viewing wires 415N, 419P. Preferably,cap 418 is made of an insulating material, such as rubber or plastic,and is designed so that it snaps onto housing 411.

[0079] Persons skilled in the art will recognize that the laser beam LBmay have a cross-section that is longer along a first axis than along asubstantially perpendicular axis. In other words, its height may belarger than its width (see, e.g., beam spot LBV in FIG. 26), etc. Thisis because the laser emission is generated by light oscillating atresonance within an active semiconductor layer, that is sandwichedbetween two internally highly reflective semiconductor faces.Collimating optics in the laser diode module 415 may reshape this lightinto a more equal-dimensioned beam. However, even after collimation, thelaser beam LB is not perfectly circular.

[0080] It is preferable thus to align the laser diode module 415 so thatthe longer axis of the beam spot is disposed substantially horizontally,i.e., along and/or coplanar to the laser light plane generated by thelaser level 10 (see, e.g., beam spot LBH in FIG. 26). This minimizes theheight of the laser beam, providing for a more exact, or “crisper,”laser light plane.

[0081] Such result can be achieved, for example, as follows. First, theorientation of the semiconductor material layers within the lasercrystal must be identified. The orientation is typically fixed withrespect to three electrical pins on the laser diode 415D. Once theorientation of the layers and pins has been identified, the printedcircuit board 415P may be designed to receive the laser diode 415D in acertain rotational position. Printed circuit board 415P may also beprovided with an indexing tab 415I. This tab 415I fits in a slot (notshown) in barrel 413, fixing the rotational position of the laser diodemodule 415 relative to the laser diode housing 411. Accordingly, thelaser diode module 415 can be consistently installed so that the longeraxis of the beam spot is disposed substantially horizontally, i.e.,along and/or coplanar to the laser light plane generated by the laserlevel 10. Persons skilled in the art shall recognize that the tab andslot may be alternative provided on barrel 413 and printed circuit board415P, respectively.

[0082] Persons skilled in the art should recognize that wall 41 ofengine assembly 40 substantially encloses and/or protects laser assembly400. Slots 41S may be disposed on wall 41 to allow laser beam LB to exittherefrom.

[0083] Preferably, laser assembly 400 has two diode modules 415. Onereason for such arrangement is the added intensity of the resultinglaser beam plane.

[0084] Another reason is that having two diode modules 415 will preventany unlighted spots on the laser beam plane. As shown in FIG. 14, theslots 41S are preferably separated by posts 41P. Preferably the width ofposts 41P is such that, when one laser diode module 415 is blocked byone post 41P, the other laser diode module 415 projects a laser beam LBthat exists through slot 41S.

[0085] As mentioned above, powering assembly 430 provides power to laserdiode modules 415. Powering assembly 430 may include a slip ring 431,which is preferably integrated. Preferably, slip ring 431 is fixedlydisposed to a floor 441. A bracket 432 may be used to fix slip ring 431unto floor 441.

[0086] Slip ring 431 may receive power through positive wire 431WP andnegative wire 431WN. The slip ring 431 may be electrically connected toa shaft 433, via brushes 431B, rendering shaft 433 with a particularelectrical potential. Shaft 433 is preferably made of metal, such assteel or aluminum. Preferably, shaft 433 has a positive voltage.

[0087] Slip ring collar 434 may be disposed at and electricallyconnected to the upper end of shaft 433. Persons skilled in the art willrecognize that slip ring collar 434 is also electrically charged. A dualconstant velocity joint (or universal joint) may connect the slip ringcollar 434 to a pulley 422, as explained below. A light spring 435 maybridge the electrical gap between the slip ring collar 434 and pulley422. Spring 435 may also slightly preload the joint to eliminatebacklash.

[0088] As mentioned above, driving assembly 420 is provided for rotatinglaser assembly 410. Driving assembly 420 may include a motor 424 drivinga shaft 424S and a pulley 424P disposed thereon. Pulley 424P may drive abelt 423, which drives pulley 422. Pulley 422 is preferably fixedlyattached to shaft 419. Accordingly, when motor 424 rotates shaft 424S,it will drive pulley 422 and rotate shaft 419.

[0089] Motor 424 may be supported by vial assembly 450, plate 451 and/orby a bracket connected thereto. The motor 424 is preferably controlledand/or driven by a pulse width modulation (PWM) circuit, which is shownin FIG. 35A as a block diagram, and in FIG. 35B as a circuit schematic.

[0090] The user adjustable voltage 601 includes a potentiometer 601P,which can be moved by a user. The potentiometer 601P varies the selectedvoltage between a top voltage representative of the top rotational speedof motor 424, and a bottom voltage, where the motor 424 does not rotate.Preferably, the bottom voltage is slightly negative.

[0091] The selected voltage is then fed to a summer 602, whichsubstracts the motor's back electromotive force (emf) feedback voltagefrom the selected voltage. The emf voltage is determined by the sampleand hold 605 as follows. Persons skilled in the art will recognize thatmotor 424 is driven by pulses. The longer and/or the more frequent thepulses, the longer the motor 424 runs on electricity, allowing it toaccelerate.

[0092] When the motor 424 is not driven by a pulse, the motor 424 actsas an inductor and creates a flyback (negative) voltage. This flybackvoltage is then shunted.

[0093] When the flyback voltage is shunted, motor 424 is freewheelingand generating voltage. In particular, motor 424 generates back emfvoltage, which is relatively proportional to the rotational speed ofmotor 424. The sample and hold 605 then samples the back emf voltage,holds it and then sends it summing junction 602.

[0094] Summing junction 602 generates an error signal which goes intocontroller 603. Controller 603 then sends a drive signal to the PWMmotor drive 604, which sends out the drive pulses to drive motor 424.The PWM motor drive 604 also sends a signal indicating that it isdriving motor 424 to the sample and hold 605. In this manner, sample andhold 605 does not sample the voltages created by motor 424 at the sametime the PWM motor drive 604 is driving the motor 424.

[0095] Sample and hold 605 also has another circuit that monitors theflyback voltage, to prevent sampling thereof. Once the flyback voltageis shunted, sample and hold 605 can sample the back emf voltage.

[0096] Persons skilled in the art should recognize that controller 603may require both positive and negative supply voltages. Since the laserlevel 10 is preferably battery powered, a voltage inverter 606 has beenprovided to invert the battery voltage, thus providing the negativesupply voltage to controller 603.

[0097] Persons skilled in the art will recognize that FIG. 35Billustrates one possible implementation of the circuit diagrammed inFIG. 35A. Persons skilled in the art will also be able to build andanalyze the operation of the circuit shown in FIG. 35B. The values ofthe different components shown in the schematics are as follow: C1  10μF C2  10 μF C3  01 μF C4  33 μF C5  22 μF C6 100 μF C7  22 μF C9  01 μFC10  10 μF D1 1N4148 D2 1N5228 D3 1N4148 D4 1N4148 D5 1N4148 D6 1N4148D7 1N5818 D17 1N4148 Q1 2N3906 Q2 2N3906 Q3 2N3906 Q4 2N3904 R1  10 KΩR2   1 KΩ R3  11 KΩ R4  20 KΩ R5  39 KΩ R6   3 KΩ R7  15 KΩ R8   3 Ω R9  1 KΩ R10   1 KΩ R11   1 KΩ R12  10 KΩ R13  10 KΩ R14  10 KΩ R15  38 KΩR16  10 KΩ R17  10 KΩ R18  10 KΩ R19  10 KΩ R21   1 KΩ R22  10 KΩ R38  1 KΩ P39  10 KΩ R43 1.1 KΩ U1 74HC4316 U2 74HC14 U3 74HC4066 U4 LM311U5 LM324 U6 LM311

[0098] Persons skilled in the art will recognize that in the circuitshown in FIG. 35B, integrated circuits U2A, U2B and U1 are configured asa switched capacitor voltage converter to generate a negative voltagefor the operational amplifier U2 and the low end of the command signal(to ensure head rotation stops when the speed adjustment potentiometer,R18, is turned off). Q1, U4 and U6 are configured as a PWM drive. Theduty cycle is controlled by the controller output (the voltage at U6,pin 2). Q3 is the motor drive transistor and Q2 combined with R8 limitthe drive current to approximately 230 mA. U3D and C9 are a sample andhold circuit. Sampling is allowed when the drive pulse is off (U2, pin8) and when the motor coil flyback pulse is over (controlled by D4, D5,D6 and Q4). R21 and C8 forms low pass filter to reduce sampling noise.U5D buffers the feedback voltage. U5C buffers the command voltage. U5Asubtracts the feedback from the command to create an error signal. U5Bis a proportional and integral controller that commands the PWMcircuitry to drive the error signal to zero. This holds the rotary headspeed constant at a speed controlled by the user adjusting R18.

[0099] Persons skilled in the art should recognize that most of thecircuit shown in FIG. 35 should be disposed within frame assembly 30.

[0100] In addition, driving assembly 420 may include a coupling link421, which is preferably disposed on slip ring collar 434. Link 421 maybe made of a non-conductive material, such as plastic. As shown in FIGS.16-18, link 421 has at least one upper protrusion 421P and at least onelower protrusion 421LP extending from a shaft 421S. Preferably, link 421has four upper protrusions 421P extending in a cross formation fromshaft 421S. Similarly, link 421 may have four lower protrusions 421LPextending in a cross formation from shaft 421S. Preferably, link 421 isinjection molded to obtain the desired shape.

[0101] Lower protrusions 421LP may be disposed in a similarly shapedarea of slip ring collar 434. Preferably, a gap 434G exists betweenlower protrusion 421LP and slip ring collar 434 to allow some rotationalplay therebetween.

[0102] Similarly, upper protrusions 421P may be disposed in a similarlyshaped area of pulley 422. Preferably, a gap 422G exists between lowerprotrusion 421LP and pulley 422 to allow some rotational playtherebetween.

[0103] Because of the shape of the protrusions 421P, 421LP, the shape ofthe slots in pulley 422 and slip collar 434, and the gaps 422G, 434Gtherebetween, rotary motion between shaft 419 and pulley 422 istransmitted through link 421 to shaft 433. Accordingly, this systembehaves like a double-knuckle joint, compensating for misalignmentbetween the slip ring 431, the shaft 433 and pulley 422 via six degreesof freedom (three translational degrees and three rotational degrees).This also minimizes stress on the slip ring 431.

[0104] Referring to FIG. 15, as mentioned above, slip collar 434 iselectrically charged. This charge may be transmitted to pulley 422 via aspring 435. Shaft 419 is then charged due to the electrical connectionbetween pulley 422 and shaft 419. Persons skilled in the art willrecognize that spring 435 may also serve to maintain alignment betweenslip collar 434 and pulley 422.

[0105] On the other hand, a wire 431N exiting slip ring 431 may carrythe opposite charge to laser diode module 415. If shaft 419 is chargedpositively, then wire 431N carries the negative charge. Wire 431Npreferably bypasses shaft 433 and slip collar 434, and enters shaft 419through pulley 422. As mentioned above, shaft 419 is hollow, allowingwire to extend therethrough until it is electrically connected to wire415N.

[0106] Referring to FIGS. 20-21, manual adjustment assemblies 460, 460′may be provided on engine assembly 40, for manually rotating laserassembly 410. Referring to FIG. 20, a plate 462 may be fixedly attachedto wall 41 of engine assembly 40. Preferably, plate 462 is riveted untowall 41. An adjustment knob 461 may be disposed between wall 41 andplate 462, and extend through the top of engine assembly 40. A spring463 is preferably disposed between knob 461 and plate 462. A plunger 465may be disposed under knob 461. Plunger 465 may extend through plate 462for contacting laser diode housing 411. Preferably, the plunger areasthat contact laser diode housing 411 are rubberized, or covered with ahigh friction material. Alternatively, plunger 465 is made of rubber.Tabs 465T may capture plunger 465 between plate 462 and knob 461. Aspring 464 may be disposed between plunger 465 and knob 461.

[0107] Accordingly, if the user wants to adjust the location of laserdiode housing 411, the user needs only to press knob 461 downwardly,forcing plunger 465 into contact with laser diode housing 411. The usercan then rotate laser diode housing 411 by rotating knob 461. The usercannot overload the laser diode housing 411 because the springpreferably 464 maintains a controlled contact force between plunger 465and laser diode housing 411. In addition, adjustment knob 461 and/orspring 463 preferably bottom out on plate 462 before spring 464 is fullycompressed.

[0108] As shown in FIG. 21, adjustment assembly 460′ is similar toadjustment assembly 460, where like numerals refer to like parts. Themain difference between the two embodiments is tha plunger 465 isretained by retaining pin 466, rather than tabs 465T contacting plate462. Preferably, pin 466 is fixedly attached to knob 461.

[0109] Referring to FIGS. 8, 14-15 and 23, vial assembly 450 preferablyhas a vial plate 451 and pedestals 452 for supporting vial plate 451 onfloor 441. Preferably, an insulation pad 452I is disposed betweenpedestals 452 and floor 441 for electrically insulating vial assembly450 from floor 441.

[0110] Vial plate 451 may carry multiple spirit vials thereon toindicate whether vial plate 451 and/or laser diode modules 415 are in asubstantially horizontal plane. Preferably, vial plate 451 carries atleast three horizontal vials 454VF, 454VS, 454VR and one vertical vial455V. The horizontal vials 454VF, 454VS, 454VR are preferably disposedon the front, right and rear walls of engine assembly 40. Vertical vial455V may be disposed on the rear wall of engine assembly 40.

[0111] Suitable vials for this application may be parts nos. 0349 and/or0224 made by Empire Level Mfg. Corp. of Milwaukee, Wis. Alternatively,the vials can be custom made by bending or grinding, as is well known inthe art, so long as the desired dimensional requirements are met.

[0112] In the present case, the main dimensional requirements for thevials are length, diameter and angular sensitivity. Persons skilled inthe art will recognize that length and diameter are dependent upon thesize of the desired vial.

[0113] As to angular sensitivity, persons skilled in the art willrecognize that the angular sensitivity of the vials is identified by“minutes”, as in “one-minute vials.” The vials used in laser level 10may be more accurate, equally accurate or less accurate than one-minutevials. Preferably, the vials used in the laser level 10 are one-minutevials, five-minute vials, six-minute vials, or any other vials with anangular sensitivity between the one-minute vials and the six-minutevials.

[0114] Such arrangement is advantageous for several reasons. First, whenengine assembly 40 is in the vertical position, the user may want tocheck vials 454VS and 454VF and/or 454VR to determine whether the laserdiode modules 415 are level. However, when engine assembly 40 is in thehorizontal position, the user may not be able to check vials 454VSand/or 454VF. The user can nevertheless confirm whether laser diodemodules 415 are substantially vertical, or “plumb,” by checking vials454VR and 455V, which are now laying subtantially horizontally on therear face.

[0115] Another reason for providing parallel vials 454VF, 454VR is toprovide redundant alignment indication. In other words, both vials maybe calibrated to indicate level when the laser beam plane is horizontal.If the laser level 10 is disturbed violently enough for one of the vialsto become uncalibrated with respect to the laser beam plane, the usercan notice such problem by comparing both vials 454VF, 454VR.

[0116] Referring to FIG. 23, vials 454VR, 455V may be attached to vialholders 454, 455. Preferably, the vials 454VR, 455V are glued withoptical glue to the vial holders 454, 455.

[0117] Vial holder 454 may be pivotally attached to vial plate 451 viapin 454P. Alternatively, vial holder 454 may be flexibly attached tovial plate 451 via a flexible junction or flexure. The flexible junctionmay be integral with vial holder 454 and/or vial plate 451, or it may bebonded to vial holder 454 and/or vial plate 451. Persons skilled in theart should recognize that the flexure may be mounted to the vial plate,and a vial may be bonded on the flexure.

[0118] An adjustment screw 454B may extend through vial plate 451 andthreadingly engage vial holder 454. A spring 454S may be disposedbetween vial plate 451 and vial holder 454. Preferably, spring 454S is acompression spring. Spring 454S may be disposed along or outside screw454B. Accordingly, when the screw 454B is rotated, vial holder 454 willpivot about pin 454P. Spring 454S will maintain the vial holder 454 inthe desired position.

[0119] Persons skilled in the art will recognize that screw 454B maythreadingly engage and extend through vial holder 454 and contact(rather than extend through) vial plate 451. Alternatively, screw 454Bmay extend through vial holder 454 and threadingly engage vial plate451.

[0120] Similarly, vial holder 455 may be pivotally attached to vialplate 451 via a pin 455P. Alternatively, vial holder 455 may be flexiblyattached to vial plate 451 via a flexible junction or flexure. Theflexible junction may be integral with vial holder 455 and/or vial plate451, or it may be bonded to vial holder 455 and/or vial plate 451.Persons skilled in the art should recognize that the flexure may bemounted to the vial plate, and a vial may be bonded on the flexure.

[0121] A pedestal or protrusion 453 may extend downwardly from vialplate 451. A screw 455B may extend through protrusion 452 andthreadingly engage vial holder 455. A spring 455S may be disposedbetween vial plate 451 and vial holder 455. Preferably, spring 455S is acompression spring. Spring 455S may be disposed along or outside screw455B. Accordingly, when the screw 455B is rotated, vial holder 455 willpivot about pin 455P. Spring 455S will maintain the vial holder 455 inthe desired position.

[0122] Persons skilled in the art will recognize that screw 455B maythreadingly engage and extend through vial holder 455 and contact(rather than extend through) vial plate 451. Alternatively, screw 455Bmay extend through vial holder 455 and threadingly engage vial plate451.

[0123] Once the vials are adjusted, the screws 454B, 455B may be lockedin place with a quick-drying adhesive, such as Loc-Tite.

[0124] Persons skilled in the art should recognize that the other vialsmay be adjusted in a similar manner.

[0125] Referring to FIGS. 24-25, persons skilled in the art should alsorecognize that a leveling mechanism 440 is preferably provided foradjusting the plane upon which laser assembly 410 rests, in order toensure that the laser beam plane is substantially horizontal orsubstantially vertical. Leveling mechanism 440 includes floor 441 uponwhich laser assembly 410 and/or vial assembly 450 rest thereon. Floor441 may be disposed over a plate 443. Plate 443 may have holes 443S forreceiving shaft 32 therethrough.

[0126] Preferably, floor 441 and plate 443 are connected. A screw 448may threadingly engage floor 441 and contact plate 443. A spring 448Smay be disposed between the head 448H of screw 448 and floor 441 forbiasing floor 441 downwardly towards plate 443. Similarly, a screw 446may threadingly engage plate 443 and contact floor 441. A spring 446Smay be disposed between the head 446H of screw 446 and plate 443 forbiasing plate 443 upwardly towards floor 441. Accordingly, the distancebetween floor 441 and plate 443 may be adjusted by rotating screws 448and/or 446. A spring 447 may also be disposed between floor 441 andplate 443.

[0127] Preferably, floor 441 carries a pitch shaft 442PS, which can berotated via pitch knob 442P. Shaft 442PS may be threadingly engaged tomoveable pitch cam 442PC, so that when shaft 442PS is rotated, moveablepitch cam 442PC travels along the longitudinal axis of pitch shaft442PS. Moveable pitch cam 442PC preferably contacts fixed pitch cam443PC of plate 443. As shown in FIG. 24, at least one of pitch cams442PC, 443PC may have ramps for forcing moveable pitch cam 442PC (andfloor 441) to move upwardly or downwardly. Persons skilled in the artshould recognize that pitch shaft 442PS and moveable pitch cam 442PC maybe disposed on plate 443, while fixed pitch cam 443PC may be disposed onfloor 441. Such arrangement allows the user to change the pitch angle offloor 441, i.e., to move the front of floor 441 upwardly while movingthe rear of floor 441, or vice versa.

[0128] Persons skilled in the art will recognize that fixed pitch cam443PC may be replaced by a pitch pin 443PP supported by walls extendingfrom plate 443. Pitch pin 443PP would function in the same manner asfixed pitch cam 443PC, except that pitch pin 443PP would be lesssensitive to any rotational or angular variance of moveable pitch cam442PC.

[0129] Floor 441 may also carry a roll shaft 442RS, which can be rotatedvia roll knob 442R. Shaft 442RS may be threadingly engaged to moveableroll cam 442RC, so that when shaft 442RS is rotated, moveable roll cam442RC travels along the longitudinal axis of pitch shaft 442RS. Moveableroll cam 442RC preferably contacts fixed roll cam 443RC of plate 443. Asshown in FIG. 25, at least one of roll cams 442RC, 443RC may have rampsfor forcing moveable roll cam 442RC (and floor 441) to move upwardly ordownwardly. Persons skilled in the art should recognize that roll shaft442RS and moveable roll cam 442RC may be disposed on plate 443, whilefixed roll cam 443RC may be disposed on floor 441. Such arrangementallows the user to change the roll angle of floor 441, i.e., to move theleft side of floor 441 upwardly while moving the right side of floor441, or vice versa.

[0130] Persons skilled in the art will recognize that fixed roll cam443RC may be replaced by a roll pin 443RP supported by walls extendingfrom plate 443. Roll pin 443RP would function in the same manner asfixed roll cam 443RC, except that roll pin 443RP would be less sensitiveto any rotational or angular variance of moveable roll cam 442RC.

[0131] Referring to FIGS. 27-29, laser level 10 preferably has a bumpsensor assembly 650 for indicating that the laser level 10 has been hitor bumped, and potentially knocked out of level alignment. Bump sensorassembly 650, and its circuit, are preferably disposed on frame assembly30.

[0132] Bump sensor assembly 650 preferably has a sensor 651. Sensor 651is preferably a thin piezoelectric element firmly mounted inside wall 32of frame assembly 30. Such element is typically used in piezoelectricbuzzers, and may consist of a thin slice of piezoceramic materialsandwiched between two electrical contact plates. When the piezoceramicelement is stressed mechanically, it generates an electrical chargeacross the contact plates. Piezoelectric elements do not typicallyrespond to steady-state stress.

[0133] Accordingly, when laser level 10 is bumped, the piezoceramicelement is stressed, which in turn generates an electrical charge acrossthe contact plates. An amplifier 652 with a preferably high inputimpedance may electrically buffer, low-pass filter and/or amplify theoutput of sensor 651. A voltage at the amplifier output exceeding apredetermined threshold, such as approximately 70% of the circuit supplyvoltage, may trigger the timing circuit 653 to activate the alarms.Timing circuit 653 may include a flip-flop. Accordingly, if theamplifier output voltage is above the threshold, the flip-flop may betripped and latched.

[0134] The timing circuit 653 then may cause a light emitting diode(LED) 656 to flash until manual reset button 654 is activated.Similarly, timing circuit 653 may disable motor 658 (which preferably ismotor 424) and/or may cause laser 657 (which preferably is laser diodemodule 415) to flash. Such alarms would indicate to the user that thelaser level 10 may be out of alignment. Again, the motor 658 and/orlaser 657 may be reset when manual reset button 654 is activated.

[0135] Bump sensor assembly 650 may also include a manual enable/disablebutton 655 for allowing the user to enable and/or disable the bumpsensor as desired.

[0136] Persons skilled in the art will recognize that FIGS. 29B-Dillustrate one possible implementation of the circuit diagrammed in FIG.29A. Persons skilled in the art will also be able to build and analyzethe operation of the circuit shown in FIG. 29D. The values of thedifferent components shown in the schematics are as follow: C1 0.01 μFC3   10 μF C4   10 μF C5   10 μF C6   10 μF C7 0.47 μF C8   22 μF C90.01 μF C11   22 μF.25 V C12  220 μF.16 V C13   22 μF.25 V C14   1 μF.25V C15   1 μF.25 V D4 1N4148 D5 1N5818 D6 1N5230 D7 1N5813 D9 1N4148 D10LM385 -1.2 D11 1N4148 D12 1N4148 D13 1N4148 D14 1N4148 L1  330 μH.1 A Q12N4401 Q2 2N4401 Q3 2N4401 Q4 2N4401 Q5 2N4401 Q7 2N4401 Q8 2N4401 Q92N4401 Q10 2N4401 R1 200 KΩ R2 100 KΩ R3 100 KΩ R4  1 MΩ R5 200 KΩ R6  1KΩ R7 330 Ω R8  10 KΩ R9  10 KΩ R10 200 KΩ R11 300 Ω R12  1 MΩ R13 330 ΩR14  75 KΩ R15  10 KΩ R16 750 KΩ R17 510 Ω R18  51 KΩ R20  10 KΩ R21  10KΩ R22 510 Ω R24  51 KΩ R25  10 KΩ R26  1 MΩ R27  1 MΩ R28  10 KΩ R29 10 KΩ R30  10 KΩ R31  51 Ω R34  10 KΩ U1 74HC74 U2 74HC123 U3 LM358 U474HC00 U5 74HC14 U6 LM555C U7 LM2574M-50 (manufactured by NationalSemiconductor Inc.)

[0137] It may be preferable to mount a mechanical amplifier assembly 660unto sensor 651. This is because piezoelectric sensor 651 typicallyresponds only to high frequency strain caused by bumps or taps. Themechanical amplifier assembly 660 would increase the sensor'ssensitivity to low frequencies by converting low frequency, i.e., slow,motions into high frequency taps which can be sensed by sensor 651.

[0138] The mechanical amplifier 660 preferably includes a base 661disposed on the piezoelectric element or wall 32, a shaft 662 extendingtherefrom, a spring 664 connected at one end to the end of shaft 662,and a mass 663 connected to the other end of spring 664. Preferably,spring 664 is trapped between head 662H and trap 662T of shaft 662.Also, spring 664 may be trapped by mass 663 via screws 663S.

[0139] Accordingly, mass 663 is preferably suspended by spring 664.Preferably, shaft 662 extends through mass 663 so that mass 663 iscentered along shaft 662. This makes the system sensitive todisturbances in all lateral directions, which would cause mass 663 totap shaft 662, creating a high frequency tap. In addition, the shaft 662may limit the motion of mass 663, which prevents over-stretching ofspring 664. Mass 663 may also travel vertically along shaft 662 to makethe sensor 651 sensitive to vertical motion. Preferably, mass 663 isdisposed close to base 661 so that mass 663 can contact base 661directly.

[0140] Referring to FIGS. 1 and 11-13, laser level 10 may be powered bya battery 60. Battery 60 may be connected to laser level 10 viaterminals 3 IT. Frame assembly 30 may have an opening 31F which allowsprotrusion 61 of battery 60 to enter frame assembly 30 and contactterminals 31T.

[0141] Preferably, battery 60 is one that is used with other powertools. Persons skilled in the art are referred to U.S. Pat. Nos.5,391,972 and 5,144,217, which are wholly incorporated by referenceherein.

[0142] Preferably, an adapter assembly 70 is used to acceptdifferently-shaped battery packs, especially those that may have thesame terminal configuration, but different pack (62) or protrusion (61)shapes. Adapter assembly 70 may include a plate 71, which is preferablymade of plastic. Plate 71 may have two opposite curved sides, which havesubstantially the same radius. Plate 71 may have a flange 71F on each ofthe curved sides. Flange 71F may be disposed along about 55°-60° of eachcurved side. Preferably, flange 71F is captured by capture walls 31C inframe assembly 30. Preferably, plate 71 has a pivot boss 71P, which maybe captured between two clamshell halves of frame assembly 30, forallowing plate 71 to pivot thereabout.

[0143] Plate 71 may have a first opening 72 and a second opening 73,which allow a first battery 60 and a second battery (not shown),respectively, to extend therethrough. Accordingly, if a user wants toinsert a first battery, the user would align first opening 72 withopening 31F. Alternatively, if the user wants to insert a secondopening, the user would rotate plate 71 to align second opening 73 withopening 31F.

[0144] Plate 71 may be provided with detent protrusions 71D, whichengage notches (not shown) disposed on frame assembly 30. Detentprotrusions 71D may be disposed on tabs 71T, which preferablyresiliently bias protrusions 71D towards engagement with the frameassembly notches. Accordingly, the two desired positions of plate 71 caneasily be located.

[0145] Persons skilled in the art shall recognize that the protrusionsand notches may alternatively be disposed on frame assembly 30 and plate71, respectively. Persons skilled in the art should also recognize thata spring can be used, instead of tabs 71T, to bias protrusions 71Dtowards the notches.

[0146] Plate 71 may also have latch notches 72L, 73L to engage thelatches 63 of the first battery 60 and the second battery (not shown),respectively. Preferably, latch notches 72L, 73L are disposed so thatthey cannot engage the latches 63 of the second battery (not shown) andthe first battery 60, respectively.

[0147] A battery ejector assembly 74 may be provided to prevent thewrong battery, i.e., the one that cannot engage the proper latch notch,from contacting terminals 31T. Battery ejector assembly 74 may include abutton 74B, which is biased by spring 74S towards the battery pack.Preferably, button 74B extends through pivot boss 71B. A clip 71C maytrap button 74B within pivot boss 71B. Accordingly, button 74B pushesthe wrong battery pack away from pivot plate 71, frame assembly 30 andterminals 31T if the battery pack cannot engage the proper latch notch.

[0148] Another aspect of the invention is laser detector 500. Lightdetectors have been heretofore applied in a variety of fields, which areconstituted such that light rays are photoelectrically detected and ameasurement result is displayed to measure the intensity of the light, alight-projected location, etc. For example, light detectors have widelybeen used in a surveying field, which are constructed such that a laserbeam is ejected from a surveying instrument body and received at anobject to be measured, and the center of the laser beam-projectedlocation is located. In the light detectors of this kind, thelight-receiving section for receiving the light and the display sectionfor displaying the measurement results on the basis of a signal from thelight-receiving section are ordinarily arranged together in the sameplane.

[0149] However, since the display section for displaying the measurementresult and the light-receiving section are arranged in the same plane inthe conventional light detectors thus constituted, a surveying person isrequired to stand exactly opposed to the display section to accuratelyread the measurement result. As a result, there occurred an extremelyinconvenient problem that the measuring light entering thelight-receiving section is interrupted by the surveying person himself.

[0150] Persons skilled in the art are hereby referred to U.S. Pat. Nos.4,934,812 and 5,486,690, which are wholly incorporated herein byreference.

[0151] According to the present invention, the light detector 500according to the present invention is used, for instance, in combinationwith a laser level 10. As shown in FIG. 30, the laser level 10 is placedon a tripod 11. As the laser diode assembly 410 rotates around aperpendicular axis thereof, laser beam LB is emitted from the laserdiode assembly 410 as a measuring light beam scanned in a horizontalplane.

[0152] The light detector 500 which is to receive the laser beam LBemitted from the laser level 10 is adapted to be attached to anappropriate upright face, such as a wall face, or a grade rod 504, heldby a user. The light detector 500 may be moved along the rod 504 todetect the height and the location of the center of the laser beam fluxwith reference to a standard plane F.

[0153] Thereby the height and the location of a point or beam to bemeasured are measured by measuring the height and/or the location of thelight detector 500, or a standard horizontal plane in which the laserbeam LB is to be scanned is determined by appropriately marking thecenter of the light flux of the laser beam LB on the grade rod 504.

[0154] FIGS. 36A-C show the light detector 500 in detail. Light detector500 may have a front face 501F and a rear face 501R. A light-receivingsection 502 may be provided on front face 501F for photoelectricallyconverting the light beam LB entering therein. Preferably,light-receiving section 502 recognizes changes in intensity, rather thanthe actual intensity, of the laser beam LB as it sweeps acrosslight-receiving section 502. A light-receiving face of thelight-receiving section 502 may be contained in substantially the sameplane as the front face 501F.

[0155] In addition, display segments 503F, 503R may be respectivelyformed on front and rear faces 501F, 501R. Preferably, the displayingface of each of the display segments 503F, 503R is substantiallycoplanar to front and rear faces 501F, 501R, respectively.

[0156] The light-receiving section 502 may be constituted by a pair ofupper and lower light-receiving segments 502A. A boundary portionbetween the light-receiving segments 502A, that is, the central positionof the light-receiving section 502, is a zone through which a standardhorizontal plane of the laser beam LB is to pass.

[0157] Light detector may have an operation switch 504 to be actuatedwhen in use.

[0158]FIG. 31 shows a circuit construction of the light detector 500. Apair of photoelectric elements 506 constituting the light-receivingsegments 502A may be connected to a processor 507. Processor 507 isadapted to compare the magnitudes of received light amounts of thephotoelectric elements 506 and to output a discrimination resultthereof. The processor 507 may be connected to a display control unit508, which is adapted to select a display pattern in compliance with theoutput from the processor 507. Persons skilled in the art will recognizethat display control unit 508 may be integrated into processor 507.

[0159] The display control unit 508 may be connected to a displaysection 509 adapted to display the display pattern responsive to theoutput from the display control unit 508.

[0160] The following constitutes an exemplary use of the light detector500. While carefully observing an indication of the display section 509,a surveying person moves the light detector 500 along grade rod 504along a substantially vertical direction, which is substantiallyperpendicular to the substantially horizontal plane of the laser beamLB. At the same time, the center position of the laser beam LB isdetermined by the following procedure.

[0161] As shown in FIG. 32A, when the light flux of the laser beam LBequally enters both the light-receiving segments 502A, that is, when thecenter of the light flux-passing zone P of the laser beam LB passesthrough an intermediate point between both the light-receiving segments502A, i.e., the center point 502C of the light-receiving section 502, afirst display pattern H1 may be indicated in the display section 503 (asshown in FIG. 33A) to show that the center of the light flux of thelaser beam LB coincides with the center point 502C of thelight-receiving section 502 of the light detector 500. Preferably,detector 500 will have notches or tabs 503T disposed thereon to indicateto the user where center point 502C is relative to the light detector500.

[0162] As shown in FIG. 32B, when the light flux-passing zone P of thelaser beam LB is deviated into the upper light-receiving segment 502A, asecond display pattern H2 may be indicated in the display section 503(as shown in FIG. 33B) to show that the center of the light flux of thelaser beam LB deviates above the center point 502C of the lightreceiving section 502. Therefore, in this case, the light detector 500should be moved upwardly.

[0163] Further, as shown in FIG. 32C, when the light flux-passing zone Pof the laser beam LB deviates into the lower light-receiving segment502A, a third display pattern H3 may be indicated in the display section503 (as shown in FIG. 33C) to show that the center of the light flux ofthe laser beam LB deviates under the center point 502C of thelight-receiving section 502 of the light detector 500. Therefore, inthis case, the light detector 500 should be moved downwardly.

[0164] Persons skilled in the art will recognize that, in each of theabove cases, the surveying person M can read the beam incidence results(the display patterns H1, H2, and H3) indicated in the display section503 on either front face 501F or rear face 501R. Therefore, themeasurement could be accurately performed from any direction withoutfear of the interruption of the measuring light beam as occurred in theconventional detectors. Thus, the present invention largely contributesto the prevention of measuring errors and enhancement of the measuringefficiency.

[0165] Referring to FIG. 31, laser detector 500 may have a sound controlunit 510 that responds to the output of processor 507. Sound controlunit 510 may control a speaker 511 and/or a piezo electric element 512.Persons skilled in the art will recognize that sound control unit 510may be integrated into processor 507.

[0166] Such arrangement provides an aural feedback to the surveyingperson. For example, processor 507 and/or sound control unit 510 may beprogrammed so that speaker 511 and/or piezo 512 will sound only when thecenter of the light flux-passing zone P of the laser beam LB passesthrough the center point 502C of the light-receiving section 502. Inaddition, processor 507 and/or sound control unit 510 may be programmedso that speaker 511 and/or piezo 512 will provide a different sound whenlaser beam LB passes outside center point 502C.

[0167] In addition, laser detector 500 may have a signal generator 513for generating a signal indicating that the laser beam LB has reacheddetector 500. Persons skilled in the art will recognize that the signalgenerator 513 may react to the output of processor 507, and/or may beintegrated into processor 507.

[0168] The signal generated by signal generator 513 may be transmittedvia an RF transmitter 514, a light source 515 or any other kind oftransmitter 516, including, but not limited to, audio transmitter,microwave transmitter, infrared transmitter, etc. For example,transmitter 516 may have an infrared source 505, which converts thesignal to be transmitted into infrared light. The resulting transmissionis then sent towards laser level 10, which may be received by receptor10R.

[0169] When laser level 10 receives the transmission, the laser level 10will oscillate shaft 219 (and laser diode module 415), thus oscillatinglaser beam LB. Preferably, laser level 10 will oscillate laser beam LBso that it forms an angle Z, which encloses laser detector 500. Angle Zmay be between about 1° and about 180°. Accordingly, a user that is onlyinterested in indicating a part of the laser beam plane can now do so byplacing a laser detector 500 in the desired portion of the plane.

[0170] Preferably, laser level 10 will have a control knob 10CK forcontrolling the amplitude of angle Z.

[0171] Alternatively, laser level 10 could just reverse the rotationaldirection of shaft 419 when it receives the transmission. Laser detector500 may have a delay programmed between the time laser beam LB contactsthe detector 500 and the time it sends the transmission to laser level10. This would allow the laser beam LB to move past laser detector 500before laser level 10 reverses direction. This generates an arc with anangle Z that could be adjusted by changing the delay time or therotational velocity of the shaft 419.

[0172] Laser level 10 could be programmed to ignore every nthtransmission, e.g., every third transmission. Accordingly, the laserlevel 10 would rotate past laser detector 500, reverse its direction androtate past laser detector 500, and reverse its direction and rotatepast laser detector 500 for a third time. Rather than reverse a thirdtime, laser level 10 would continue rotating shaft 419 until it contactslaser detector 500, or a second laser detector. Accordingly, laser level10 would highlight one laser detector 500, then the other, etc.

[0173] Persons skilled in the art may recognize other alternatives tothe means disclosed herein. However, all these additions and/oralterations are considered to be equivalents of the present invention.

What is claimed is:
 1. A light detector comprising: a housing havingfront and rear walls; a light receiving section disposed on the frontwall; and displays disposed on the front and rear walls for showing thelocation of received light relative on the light receiving section.
 2. Acordless device connectable to a first battery pack having a firstbattery housing, a first terminal block supported by the first batteryhousing and a first latch mechanism disposed at a first distance fromthe first terminal block, a second battery pack having a second batteryhousing, a second terminal block supported by the second battery housingand a second latch mechanism disposed at a second distance from thesecond terminal block, said first and second distances being different,the device comprising: a housing; a receptacle disposed within thehousing for electrically connecting to the first and second batterypacks; a plate movably connected to the housing, the plate having firstand second latch recesses, the plate being movable between a firstposition where the distance between the receptacle and the first latchrecess is substantially equal to the first distance so that the firstbattery pack can be electrically connected to the receptacle and latchedto the first latch recess, and a second position where the distancebetween the receptacle and the second latch recess is substantiallyequal to the second distance so that the second battery pack can beelectrically connected to the receptacle and latched to the second latchrecess.
 3. The cordless device of claim 2, wherein the plate isrotatable between the first and second positions.
 4. The cordless deviceof claim 2, wherein the first and second battery packs have differentvoltages.
 5. The cordless device of claim 2, wherein the first andsecond battery pack have the same terminal block configuration.
 6. Thecordless device of claim 2, further comprising a battery ejectorassembly for biasing a battery pack away from the receptacle.
 7. Thecordless device of claim 2, further comprising a button disposed on thehousing and extending through the plate for contacting a battery pack,and a spring biasing the button away from the receptacle.
 8. A laserlevel comprising: a main housing; a laser housing pivotally attached tothe main housing, the laser housing being pivotable about 90° relativeto the main housing; a motor disposed in the laser housing; a shaftdriven by the motor, the shaft having a longitudinal axis; and at leastone diode disposed on the shaft for projecting a laser beam, wherein thelaser beam is substantially perpendicular to the shaft.
 9. The laserlevel of claim 8, further comprising a locking means for fixing theangular position of the laser housing.
 10. A laser level comprising: ahousing; a motor disposed in the housing; a shaft driven by the motor,the shaft having a longitudinal axis; at least one diode disposed on theshaft for projecting a laser beam, wherein the laser beam issubstantially perpendicular to the shaft; and a first power tool batterypack electrically connected to the motor and removably attached to thehousing.
 11. The laser level of claim 10, further comprising a secondpower tool battery pack electrically connected to the motor andremovably attached to the housing.
 12. The laser level of claim 11,wherein the first and second battery packs have different voltages. 13.The laser level of claim 11, wherein the first and second battery packhave the same terminal block configuration.
 14. A laser levelcomprising: a main housing; a motor disposed in the main housing; ashaft driven by the motor, the shaft having a longitudinal axis; a diodehousing disposed on the shaft; and at least one diode disposed in thediode housing for projecting a laser beam, wherein the laser beam issubstantially perpendicular to the shaft; wherein the main housingcomprises an upper portion covering the diode housing.
 15. The laserlevel of claim 14, further comprising a plunger disposed on the upperportion of the main housing movable between a first position contactingthe diode housing and a second position not contacting the diodehousing.
 16. The laser level of claim 15, wherein the diode housing canbe rotated by rotating the plunger when the plunger is in the firstposition.
 17. The laser level of claim 15, further comprising a springfor biasing the plunger towards the second position.
 18. A laser levelcomprising: a main housing; at least one diode disposed in the housingfor projecting a laser beam, said beam being rotatable to denote areference plane; and a protective bar flexibly connected to the mainhousing.
 19. The laser level of claim 18, further comprising a handleattached to the protective bar.
 20. The laser level of claim 18, furthercomprising a connector assembly flexibly connecting the protective barto the main housing.
 21. The laser level of claim 20, wherein theconnector assembly comprises a flexible gasket.
 22. The laser level ofclaim 21, wherein the flexible gasket is disposed between the protectivebar and the main housing.
 23. A laser level comprising: a main housing;at least one diode disposed in the housing for projecting a laser beam,said beam being rotatable to denote a reference plane; and a clampassembly slidably attached to the main housing for clamping the laserlevel to an architectural feature.
 24. A method for constructing a laserlevel comprising the steps of: providing a housing, a motor disposed inthe housing, a shaft driven by the motor, the shaft having alongitudinal axis, at least one diode disposed on the shaft forprojecting an elliptical laser beam with major and minor axes, whereinthe laser beam is substantially perpendicular to the shaft; and aligningthe at least one diode so that the major axis of the elliptical laserbeam is substantially horizontal.